The production of a polycarboxylic acid-based polymer through the polymerization of a monomer composition containing an unsaturated monocarboxylic acid-based monomer, such as (meth)acrylic acid (salt), or an unsaturated dicarboxylic acid-based monomer, such as maleic acid (salt), has been performed (see, for example, Patent Literatures 1 and 2).
In the production of such polycarboxylic acid-based polymer, the foaming of a polymerization reaction liquid may occur. Such foaming occurs in the production of, for example, a homopolymer of the unsaturated monocarboxylic acid-based monomer, a homopolymer of the unsaturated dicarboxylic acid-based monomer, a copolymer of the unsaturated monocarboxylic acid-based monomer and the unsaturated dicarboxylic acid-based monomer, a copolymer of the unsaturated monocarboxylic acid-based monomer and a sulfonic group-containing ether compound, such as sodium 3-allyloxy-2-hydroxy-1-propanesulfonate (hereinafter sometimes referred to as “HAPS”), or a copolymer of the unsaturated monocarboxylic acid-based monomer, the unsaturated dicarboxylic acid-based monomer, and the sulfonic group-containing ether compound. In particular, the foaming occurs remarkably in the production of, for example, the copolymer of the unsaturated monocarboxylic acid-based monomer, the unsaturated dicarboxylic acid-based monomer, and the sulfonic group-containing ether compound.
Such foaming of the polymerization reaction liquid as described above does not become a large problem when small-scale foaming occurs. However, when large-scale foaming occurs, a reaction vessel is filled with the foamed polymerization reaction liquid, and hence the original loading amount of the polymerization reaction liquid needs to be reduced as compared to a scheduled amount. Accordingly, a problem in that productivity reduces occurs.